A device of this type is known from U.S. Pat. No. 4,925,444. The prior-art infusion system offers the possibility of metering different solutions from fluid sources according to the multiplex method into a common collecting channel. A typical metering cycle at a rate of metering of 50 mL per hour lasts about 40 sec. If the cycle time is reduced, a higher flow rate is necessary, which is permissible as a short-term bolus in exceptional cases only.
Catecholamines with blood plasma half-lives of less than 2 minutes must be metered either continuously or quasi-continuously at intervals shorter than 15 sec. The smallest metered quantity is about 1 μL.
Other drugs are titrated by the physician according to their action; for example, in the case of remifentanil, the rate of metering is changed as a function of the depth of anesthesia. A change in the rate of metering must have reached the patient within a few seconds in the case of these drugs. Such drugs cannot be metered with the prior-art infusion system because of the long rinsing times. Incompatible drugs can also be transported through the same patient line in exceptional cases only with the prior-art infusion system. The desired separation between individual drugs can be achieved with difficulty only. A parabolic flow profile will rather develop in the patient line, which leads to nearly complete mixing on the transport path.